The present invention is generally related to a vacuum freeze-drying apparatus and a frozen particle manufacturing method.
FIG. 6 is an internal configuration view of a conventional vacuum freeze-drying apparatus.
A vacuum freeze-drying apparatus 100 includes a vacuum tank 111, a collection tank 112 disposed below the vacuum tank 111, a pipe 121 provided respectively with first and second openings 122 and 124 at one end and the other end, the first opening 122 being exposed inside the collection tank 112 and the second opening 124 being exposed inside the vacuum tank 111, and a valve element 115 that switches between blocking and opening the first opening 122.
A valve seat 123 having ring-shape is adhered to and fixed onto the other end of the pipe 121 so as to surround the first opening 122. The valve seat 123 is, for example, a rubber O-ring.
The valve element 115 is disposed below the valve seat 123. When the surface of the value element 115 is pressed against the valve seat 123 and closely adhered thereto in a ring-shape, the first opening 122 is blocked; whereas, when the surface of the valve element 115 is separated from the valve seat 123, the first opening 122 is opened.
Vacuum evacuation units 113a and 113b are connected to the vacuum tank 111 and the collection tank 112, respectively; and vacuum ambiences are created within the vacuum tank 111 and the collection tank 112.
When a raw material liquid is injected from an injector 116 into the vacuum tank 111, which has been vacuum evacuated, a liquid component evaporates from the injected raw material liquid, the raw material liquid is instantaneously cooled, and frozen particles are produced. The produced frozen particles are piled up on the surface of a heating/cooling shelf 117.
When the heating/cooling shelf 117 is tilted, the frozen particles that have collected thereon slide off from the surface of the heating/cooling shelf 117 and fall into the second opening 124.
If the first opening 122 is opened, the frozen particles pass through the inside of the pipe 121 and are transferred into the collection tank 112.
A part of the frozen particles pass through the first opening 122; and when they are released into the collection tank 112, they are in contact with the valve seat 123 and adhere thereto.
After the frozen particles have been transferred into the collection tank 112, the valve element 115 is pressed against the valve seat 123 so as to block the first opening 122. The inside of the collection tank 112 is opened to the air atmosphere, or a compressed gas is fed into the collection tank 112 from a gas introduction part (not shown); and the frozen particles are carried out from the inside of the collection tank 112.
If the frozen particles adhere to the valve seat 123, the frozen particles may become sandwiched between the valve element 115 and the valve seat 123; and thus, a gap may occur even if the valve element 115 is pressed against the valve seat 123. Thus, there has been a problem in that leaks (air leaks) occur inside the vacuum tank 111 when the inside of the collection tank 112 is opened to the air atmosphere; and as a result, the vacuum freeze-drying performance is decreased. See, for example, JPA 2004-232883.